Dynamic Cracking and Energy Absorption in Laminates Containing Through- Thickness Reinforcement

摘要

Inertial effects in the mechanism of fiber pullout were examined, with emphasis on how the rate of propagation of stress waves along the fiber, and thence the pullout dynamics, are governed by friction and the propagation of companion waves excited in the matrix. The frictional sliding between the fiber and the matrix is described by a constant interfacial friction stress, the sign of which depends on the relative particle velocity of the fiber and the matrix. The analytical results also were validated by detailed numerical finite element calculations with a cohesive law simulating interfacial friction. In addition to the theoretical work, through a sub-contract to ETech, the authors performed fundamental experiments to investigate the process of dynamic interfacial debonding and fiber push-in, especially in 2D model composite systems. With the use of high-speed diagnostics, a quantitative comparison was made between the experimental observations and the theoretical results, and they show excellent agreement. Steady state crack propagation characteristics in through-thickness reinforced laminate structures was mapped out in terms of controllable loading and material parameters, including the crack velocity and the properties of the through-thickness reinforcement. The paper includes a list of 17 publications prepared under this contract and a list of participating scientific personnel. Six of the publications prepared under this contract are appended: Delamination Dynamics in Through-Thickness Reinforced Laminates with Application to DCB specimen; Stick, Slip and Reverse Slip Characteristics during Dynamic Fiber Pullout; Inertial Effects in the Pullout Mechanism during Dynamic Loading of a Bridged Crack; Computation of Dynamic Crack Energy Release Rate for Orthotropic Systems; The Physics of Dynamic Fiber Push-In Opposed by Friction; and Modern Topics and Challenges in Dynamic Fracture.